I understand you received a timely reply from your professional services contact, but for everyone else, let's answer this question here.

At any step within your model, you can exclude an empty record by filtering on any column within the record. You would not need to multi-select different columns within the record to do so.

If you want to purge rows which only have undefined values (FNFs) in more than one column, you can create a map operation that creates a new column and populates it with the results of logical checks using the "exists" function, and then filter rows based on this new column.